High speed transmission cable

ABSTRACT

The present invention relates to a high speed transmission cable that includes a first conductor set, a dielectric film at least partially concentrically disposed around the first conductor set and a pinched portion forming an insulating envelope around the first conductor set. The dielectric film includes a base layer having a plurality of first protrusions formed on a first major surface of the base layer, wherein the dielectric film is disposed such that the base layer is partially concentric with the conductor set and wherein a portion of the first protrusions is disposed between the first conductor set and the base layer in a region where the base layer is concentric with the first conductor set.

TECHNICAL FIELD

The present disclosure relates generally to shielded electrical cablesfor the transmission of electrical signals. In particular, the presentinvention relates to high speed electric cables that can include astructured dielectric layer adjacent to the current carrying internalconductors of the cable.

BACKGROUND

Electrical cables for the high speed transmission of electrical signalsare well known. One common type of electrical cable is a coaxial cable.High speed transmission cables generally include an electricallyconductive central conductor(s) or wire(s) surrounded by an insulatingdielectric layer. An exemplary high speed transmission cable is acoaxial cable. In a coaxial cable, the electrically conductive conductorand insulating dielectric layer can further include an outer conductorand a protective outer jacket.

The insulating dielectric layer can be composed of any material orcombination of materials that electrically separate the centralconductor from other conductors within the cable. The materialproperties of the dielectric layer can significantly affect thetransmission of the electrical signal along the length of a high speedtransmission cable. Minimal interaction between the electric field andthe dielectric layer is generally desired to maintain the signalintegrity and to reduce the capacitance of the electrical signal.Capacitance slows the propagation rate of the electrical signal andreduces the signal strength. Additionally, capacitance is a strongcontributor to the cable's impedance, and therefore the dielectric layerhas the role of influencing the magnitude and uniformity of the cableimpedance, which is generally desired to be a constant along the lengthof a given insulated wire. Key electrical properties influenced by thematerial properties of the dielectric layer include signal attenuation,signal propagation rate, capacitance per given cable length, impedance,and the uniformity of these electrical properties along the length ofthe cable. Conversely, it may be desirable for the cable to haveprescribed electrical properties, such as a known impedance value.Prescribing these electrical properties will impact the structure anddimensions of the dielectric layer. The dielectric structure and thematerial's dielectric constant will directly influence the requiredthickness of the dielectric layer and hence the cable diameter, thecable flexibility, and related properties.

For example, the velocity of propagation (VOP) of electrical signalalong a coax cable relative to the speed of the electrical signal alonga conductor surrounded by air is:

${VOP} = \frac{1}{\sqrt{ɛ_{eff}}}$

where ε_(eff) is the effective dielectric constant of the dielectriclayer surrounding the central conductor. The dielectric constant of airis virtually equal to one while solid dielectric materials have adielectric constant of greater than one. In order to maximize thevelocity of propagation of the electrical signal, the effectivedielectric constant of the dielectric layer should be minimized. Theinclusion of air into the dielectric layer is one way to reduce theeffective dielectric constant of the dielectric layer.

Although electrical properties of the transmission cable generallyimprove with the incorporation of air into the dielectric structure, airalone (at ambient pressure) can not provide adequate support tocounteract external forces that can be applied to the cable duringmanufacture, installation and use of the cable. Failure to support theexternal load at any point can result in local distortions of thespacing between the central conductor and surrounding structures of thecable, thereby changing the distribution of the electric and magneticfields around the central conductor, creating local impedance changeswhich can result in signal reflections and degraded signal integrity. Ifthese distortions are significantly large (like a kink in the cable) ornumerous, the cable may no longer be suitable as a high speedtransmission line. Because air alone is not a sufficient support, thedielectric layer will also include a higher stiffness material form andmaintain the space between the inner conductor and the surroundingstructures of the cable.

Three types of dielectric layer structures which include a significantamount of air surrounding the central conductor are routinely practicedin the art: A) foamed and expanded polymers, B) thin helically woundmonofilaments and, C) axially-extruded channels.

Foamed or expanded structures can have air content up to about 70%resulting in an effective dielectric constant to 1.3-1.5. However, thestiffness of the resulting dielectric layer can be quite low, and mayfail to provide sufficient support to the central conductor underapplied loads and may allow the central conductor to kink when tightlybent. When loaded, these structures readily buckle and crush.

The helically-wound structures typically utilize a monofilament ordeviations thereof that are wrapped around a central conductor. Aninsulator tube is extruded over the wrapped conductor structure. Thesehelically-wound structures can also have low effective dielectricconstants (˜1.3), but typically provide support against external forcesat one point around the circumference of the central conductor at anygiven cross-section. This individual contact point can also beinsufficient to support external load exerted at any point around thecircumference of the central conductor that is not directly adjacent tothe wrapped filament which can lead to local deformations or kinking ofthe central conductor on bending and result in attendant signalintegrity issues.

The third type of dielectric layer structures which include asignificant amount of air are longitudinally extruded structures formedalong the conductor axis with a modified extrusion tip. These extrudedstructures can generally result in an effective dielectric constant of1.45 or higher, but the axial extrusion process of a molten polymer isnot well-suited to providing small, closely-spaced features sincesurface tension and the dynamics of extruding a liquid material in thismanner drives rounding of the features. Additionally, this processcannot readily form features that vary along the axial direction, (i.e.each cross section profile is the same). Also, the process is limited tomaterials that can be extruded around a conductor at the requiredthickness.

In summary, the prior art dielectric structures do not have sufficientability to provide low effective dielectric constants combined withsufficient mechanical integrity and design flexibility. A need existsfor high speed transmission cables that include a dielectric layer thatincorporates a significant amount of air adjacent to and around thecentral conductor while providing more uniform support around thecentral conductor resulting in a dielectric layer having greatermechanical stability while simultaneously having a low effectivedielectric constant.

SUMMARY

In one aspect, the present invention provides a high speed transmissioncable includes a first conductor set, a dielectric film at leastpartially concentrically disposed around the first conductor set and apinched portion forming an insulating envelope around the firstconductor set. The first conductor set includes one or moresubstantially parallel inner conductors defining a longitudinal axis ofthe transmission cable. The dielectric film includes a first edge and asecond edge longitudinally aligned with the first conductor set. Thedielectric film includes a base layer having a plurality of firstprotrusions formed on a first major surface of the base layer, whereinthe dielectric film is disposed such that the base layer is partiallyconcentric with the conductor set and wherein a portion of the firstprotrusions is disposed between the first conductor set and the baselayer in a region where the base layer is concentric with the firstconductor set.

In another aspect, the present invention provides a high speedtransmission cable that includes a first conductor set having twoparallel inner conductors defining a longitudinal axis of thetransmission cable, a dielectric film at least partially concentricallydisposed around the first conductor set wherein a portion of thedielectric film is disposed between the two parallel inner conductors.The dielectric film includes a base layer having a plurality of firstprotrusions formed on a first major surface of the base layer, whereinthe dielectric film is disposed such that the base layer is partiallyconcentric with the first conductor set and wherein a portion of thefirst protrusions is disposed between the first conductor set and thebase layer in a region where the base layer is concentric with the firstconductor set.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The Figures and detailed description that follow below moreparticularly exemplify illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show three isometric views of exemplary high speedtransmission cables according to an aspect the present invention;

FIG. 2 shows an isometric view of an alternative exemplary high speedtransmission cable according to an aspect the present invention;

FIGS. 3A-3D show four isometric views of exemplary dielectric films thatcan be used in a high speed transmission cable according to an aspectthe present invention;

FIGS. 4A-4D show four cross sectional views of exemplary dielectricfilms of FIGS. 3A-3D, respectively;

FIGS. 5A-5C show three additional cross sectional views of exemplarydielectric films that can be used in a high speed transmission cableaccording to an aspect the present invention;

FIGS. 6A-6D show schematic cross sectional views of a portion of fourexemplary alternative high speed transmission cables according to anaspect the present invention;

FIGS. 7A-7B show schematic cross sectional views of a portion of twoexemplary alternative high speed transmission cables according to anaspect the present invention;

FIGS. 8A-8B show a schematic representation of one method of producingan exemplary high speed transmission cable according to an aspect thepresent invention;

FIGS. 9A-9D show schematic cross sectional views of a portion of fourexemplary alternative high speed transmission cables according to anaspect the present invention;

FIGS. 10A-10C show schematic cross sectional views of a portion of threeexemplary alternative high speed transmission cables according to anaspect the present invention;

FIGS. 11A-11B show two alternative isometric views of a secondembodiment of exemplary high speed transmission cable according to anaspect the present invention;

FIGS. 12A-12E show schematic cross sectional views of a portion of fiveexemplary alternative high speed transmission cables according to anaspect the present invention;

FIGS. 13A-13D show schematic cross sectional views of a portion of fouradditional exemplary alternative high speed transmission cablesaccording to an aspect the present invention;

FIG. 14 is a schematic representation of an exemplary fabricationprocess for creating a high speed transmission cable in accordance withthe current invention; and

FIGS. 15A-15D are cross sectional views of an exemplary forming toolused in the fabrication process of claim 14.

DETAILED DESCRIPTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof.The accompanying drawings show, by way of illustration, specificembodiments in which the invention may be practiced. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the invention isdefined by the appended claims.

The present invention is directed to a high speed transmission cablehaving a structured dielectric film(s) formed around the internalconductors to create electrical transmission lines with higherpropagation speed, lower weight, and smaller size (and higher density)as well as greater dielectric constant consistency and greater crushresistance than conventional cable designs. The structured dielectricfilm(s) create air spaces around the inner conductors. In one exemplaryaspect, these structured dielectric films include a multilayer baselayer having protrusions formed on at least a portion of one majorsurface, where in at least one of the sub-layer within the base layer isan electrically conductive shielding layer.

Incorporating air into a primary dielectric material in a transmissionline can provide a number of benefits including reduction in weight,reduction in the loss contributed by the dielectric material, and areduction in the dielectric constant of the resulting dielectric film.The dielectric constant reduction in turn increases the signalpropagation rate and reduces the dielectric thickness needed for a givenimpedance and therefore the transmission cable can be smaller. A commonmethod for incorporating air is to foam the insulating material, but theresulting material can crush easily and the air content is frequentlydispersed heterogeneously through the insulating material resulting in adielectric material having a non constant dielectric constant. Theinsulating material used in the present invention is a structureddielectric film where the air is incorporated in a repeating orstructured way into the transmission cable.

FIG. 1A illustrates an exemplary embodiment of a high speed transmissioncable 100A according to an aspect of the present invention. The highspeed transmission cable includes a first conductor set 110, a firstdielectric film 120A at least partially concentrically disposed aroundthe first conductor set, a second dielectric film 130A at leastpartially concentrically disposed around the first conductor setopposite the first dielectric film and a pinched portion joining thefirst and second dielectric films. The first conductor set includes oneinner conductor 111 defining a longitudinal axis of the transmissioncable. The first inner conductor can be a bare conductor in the form ofa metallic ribbon or wire, a coated conductor comprising an innerconductive core 112 and an insulating layer 114 surrounding the innerconductive core or a coaxial cable.

The first dielectric film 120A includes a first edge 121 a and a secondedge 121 b longitudinally aligned with the first conductor set 110. Thefirst dielectric film includes a base layer 122 having a plurality offirst protrusions 124 formed on a first major surface of the base layer,wherein the first dielectric film can be disposed such that the baselayer is partially concentric with the conductor set and wherein aportion of the first protrusions is disposed between the first conductorset and the base layer in a region where the base layer is concentricwith the first conductor set.

The second dielectric film 130A can be similar the first dielectric film120A in that the second dielectric film includes a first edge 131 a anda second edge 131 b longitudinally aligned with the first conductor set110. The second dielectric film includes a base layer 132 having aplurality of first protrusions 134 formed on a first major surface ofthe base layer. The second dielectric film can be disposed partiallyconcentric with the conductor set opposite the first dielectric filmsuch that the base layer of the second dielectric film is partiallyconcentric with the conductor set and wherein a portion of the firstprotrusions of the second dielectric film are disposed between the firstconductor set and the base layer of the second dielectric in a regionwhere the base layer is concentric with the first conductor set.

The pinched portions extends parallel with the longitudinal axis of theconductor set and forms an insulating envelope 140A around the firstconductor set 110 by joining the first and second layers 120A, 130A.FIG. 1A shows the first and second dielectric films 120A, 130A oftransmission cable 100A can be joined together by the interlockingprotrusions of the first dielectric film with the protrusions 134 ofsecond dielectric film 130A in pinched portion 150A. Alternatively, anadhesive layer may be disposed between the first and second dielectricfilms within the pinched portion of the cable to form the transmissioncable. This latter aspect can reduce the need for precise registrationbetween the first and second dielectric films and the conductor setwhich they enclose. FIG. 1B shows the first and second dielectric films120B, 130B of transmission cable 100B can be joined together by bondingthe first dielectric film to the second dielectric film in a bondingregion 152B by and adhesive or fusion bonding the first and seconddielectric films at a sufficient temperature and pressure to cause theprotrusions to melt and flow together to form the bonding region inpinched portion 150B. FIG. 1C shows a transmission cable 100C havingprotrusions 124, 134 formed on the first and second dielectric films120C, 130C, respectively, only in the region of the insulating envelope140C between pinched portions 150C. The first and second dielectricfilms 120C, 130C of transmission cable 100C can be joined together bybonding the first dielectric film to the second dielectric film in abonding region 152C by thermal welding of the base layer of the firstand second dielectric films.

FIG. 2 illustrates an exemplary embodiment of a high speed transmissioncable 200 according to an aspect of the present invention that includesa first conductor set 210, a first dielectric film 220 at leastpartially concentrically disposed around the first conductor set, asecond dielectric film 230 at least partially concentrically disposedaround the first conductor set opposite the first dielectric film and apinched portion joining the first and second dielectric films. The firstconductor set 210 includes two inner conductors 211 defining alongitudinal axis of the transmission cable. The inner conductors can becoated conductors comprising an inner conductive core and on insulatinglayer surrounding the inner conductive core or coaxial cables. The firstand second dielectric films 220, 230 of transmission cable 200 can bejoined together by bonding the first dielectric film to the seconddielectric film in a bonding region 252 by an adhesive or fusion bondingthe first and second dielectric films at a sufficient temperature andpressure to cause the protrusions to melt and flow together to form thebonding region in pinched portion 250.

FIGS. 3A-3D, 4A-4D and 5A-5C illustrate dielectric films that can beused in a high speed transmission cable according to an aspect thepresent invention.

FIG. 3A is schematic drawing of a first exemplary dielectric film 320Ahaving a characteristic cross-section as shown in FIG. 4A. Dielectricfilm 320A includes a base layer 322A having a plurality of firstprotrusions 324A formed on a first major surface of the base layer. Inone exemplary aspect, the base layer of the dielectric film is acontinuous sheet of material while in another aspect the base layer canbe a perforated sheet of material. The first protrusions have a firstgeometry characterized by a first critical dimension. First protrusions324A are in the form of longitudinally extending ridges wherein thecritical dimension is the height of the ridge. When dielectric film 320Ais used in a transmission cable the height of the first protrusionscontrols the separation between the conductor set and the base layer ofthe dielectric film. Increasing the height of the ridges can increasethe amount of air between the base layer and the first conductor setwhich can lower the effective dielectric constant of the structuraldielectric film. Additionally, the pitch of the first protrusions can beused to adjust the amount of air space within the dielectric film.Decreasing pitch results in adjacent protrusions being placed closertogether and results in a decrease in the amount of airspace in thedielectric film. Alternatively, the geometry of the first protrusion canbe one of a post (protrusion 324D in FIGS. 3D and 4D), a continuousridge, a discontinuous ridge, a bump, a pyramid and any other threedimensional polygonal shape. The protrusions may be solid, hollow orcontain an internal air pocket.

In an alternative aspect, the dielectric film can have a plurality offirst protrusions and second protrusions formed on a first major surfaceof the base layer as shown in FIGS. 3B, 3C, 4B, and 4C. FIGS. 3B and 4Bshow an isometric and a cross-sectional view, respectively, ofdielectric film 320B which includes a base layer 322B having a pluralityof first protrusions 324B and a plurality of second protrusions 325Bformed on a first major surface of the base layer. The first protrusionshave a first geometry characterized by a first critical dimension andthe second protrusions have a second geometry characterized by a secondcritical dimension. First protrusions 324B and second protrusions 325Bare in the form of continuous longitudinally extending ridges.

The critical dimension of the first protrusions is again the height ofthe ridge which controls the separation between the conductor set andthe base layer of the dielectric film. The second protrusions aresmaller than the first protrusions and can serve to reinforce the baselayer to prevent buckling or kinking of the dielectric film allowing thefirst protrusions to be spaced further apart.

FIGS. 3C and 4C show an isometric and a cross-sectional view,respectively, of dielectric film 320C which includes a base layer 322Chaving a plurality of first protrusions 324C and a plurality of secondprotrusions 325C formed on a first major surface of the base layer. Thefirst protrusions have a first geometry characterized by a firstcritical dimension and the second protrusions have a second geometrycharacterized by a second critical dimension. First protrusions 324B arein the form of continuous longitudinally extending ridges while thesecond protrusions are in the form of transverse discontinuous ridgesthat are disposed between the first protrusions. The critical dimensionof the first protrusions is again the height of the ridge which controlsthe separation between the conductor set and the base layer of thedielectric film. The second protrusions are smaller than the firstprotrusions and can serve to reinforce the base layer to preventbuckling or kinking of the dielectric film allowing the firstprotrusions to be spaced further apart.

In another alternative aspect, the dielectric film can have a pluralityof first protrusions formed on a first major surface of the base layerand a plurality of second protrusions formed on a second major surfaceof the base layer as shown in FIGS. 5B and 5C. FIG. 5B shows across-sectional view of dielectric film 420B which includes a base layer422B having a plurality of first protrusions 424B formed on a firstmajor surface of the base layer and a plurality of second protrusions425B formed on a second major surface of the base layer. The firstprotrusions have a first geometry characterized by a first criticaldimension and the second protrusions have a second geometrycharacterized by a second critical dimension. The critical dimension ofthe first protrusions is the height of the ridge which controls theseparation between the conductor set and the base layer of thedielectric film. The critical dimension of the second protrusions isalso the height of the ridge which controls the separation between thebase layer and any supplemental layer (e.g. a shielding layer orprotective insulating layer) or element (e.g. a drain wire or spacer)disposed adjacent to the second major surface of the dielectric film.

Base layer of the dielectric film can be one of an insulating film, ametal foil, a bilayer structure such as bilayer structure 421 (shown inFIG. 5A) which can be composed of an insulating film 422A and a metallayer 427, or another multilayer material. One exemplary multilayermaterial can have a buried conductor layer between two insulatinglayers. Another exemplary multilayer material can have a plurality ofconductor layers separated by insulating layers.

The dielectric film can be formed by a variety of processes known in theart including extrusion, embossing, casting, lamination, and moldingprocesses. The base layer and protrusions may be formed simultaneouslyby an extrusion process from a melt processable dielectric material,such as a thermoplastic resin, utilizing an appropriate die profile.When produced by an extrusion process, the protrusions and the baselayer may be formed of a single material or the base layer may be formedof a first material and the protrusions may be formed of a secondmaterial by a co-extrusion process.

Alternatively, the protrusions of the dielectric film can be created byembossing the protrusions into the base layer. The base layer can be afilm substrate of a dielectric material that softens at elevatedtemperatures or a partially cured dielectric material that can be crosslinked after the film substrate is contacted with an embossing platen ormold on which an imprint of the protrusions has been formed. When anembossing process is used, the protrusions and the base layer will beformed of a single material.

In another alternative aspect, a melt processable dielectric material ora curable dielectric material can be dispensed on to a textured mold orroller. After cooling or curing, the material can be removed from themold or roller yielding the structured dielectric film. In this way, thebase layer and the protrusions can be formed simultaneously. In analternative aspect, a premade film substrate may be used as the baselayer. A melt processable dielectric material or a curable dielectricmaterial can be dispensed between the base layer and a textured mold orroller. After cooling or curing, the material can be removed from themold or roller yielding the structured dielectric film. In this way, theprotrusions can be formed either of the same material as the base layeror can be a different material. For example, the protrusions can beformed by casting a curable monomer or prepolymer between the mold andan existing base layer film, followed by a UV or thermal cure.

Exemplary premade film substrates for the base layer can includepolyimide films, polyester films, polyolefin films, fluoropolymer films,poly carbonate films, polyethylene naphthalate films, ethylene propylenediene monomer rubber films, liquid crystal polymer films, polyvinylchloride films, and the like. In one exemplary aspect, premade filmsubstrates for the base layer can be a metallized polymer film, such asa metallized polyimide or polyester film. Alternatively, base layer canbe a metal foil, (e.g. a copper foil) or other planar conductivematerial that can be used as a substrate for forming the dielectricfilm. In yet another aspect, the base layer can be a material composedof two or more individual layers that have been laminated together toform a striated base layer.

When a base layer is a metal foil or includes a metallic sub-layer, thesub-layer can be used as a ground plane when the dielectric filmcontaining the metallic sub-layer is used to form a high speedtransmission cable. Integration of the ground plane into the dielectricfilm eliminates the need for a separate additional ground plane as wellas potentially eliminating some or all of the dielectric materialbetween the central conductor and the ground plane such as the case whenthe base layer is composed solely of a metallic foil or when the firstmajor surface of the base layer on which the protrusions are formed ismetallic. In either of these two aspects, the dielectric properties ofthe film arise from the protrusions and air that are disposed betweenthe metallic surface of the base layer and the first conductor set.

Exemplary melt processable dielectric materials include polyolefinresins, fluoropolymer resins, polycarbonate resins, nylon resins,thermoplastic elastomer resins, ethylene vinyl acetate copolymer resins,polyester resins, and liquid crystal polymer resins.

Exemplary curable dielectric materials include thermoset resinsincluding epoxies, silicones, and acrylates, or cross-linkableprepolymer.

FIGS. 1A-1C and FIG. 2 show exemplary high speed transmission cablesthat include only one conductor set. In alternative aspects of theexemplary high speed transmission cables, the cables can have aplurality of spaced apart conductor sets.

FIGS. 7A-7B show a portion of two alternative high speed transmissioncable designs having a plurality of spaced apart conductor sets. Thesetypes of cable assemblies can be referred to as higher ordertransmission cables. Higher order transmission cables can be formed fromone or more cable sub-units. A cable sub-unit can be defined as aportion of a cable that includes one or more insulating envelopescontaining a conductor set.

FIG. 7A illustrates a portion of an exemplary high speed transmissioncable 600 according to an aspect of the present invention that includesa first conductor set 610 a, a second conductor set 610 b and firstdielectric film 620 at least partially concentrically disposed aroundthe first and second conductor sets. The first and second conductor setsare spaced apart by pinched portions 650 a, 650 b which form insulatingenvelopes 640 a, 640 b. The first conductor set 610 a includes one innerconductor 611 a defining a longitudinal axis of the transmission cableand the second conductor set includes four inner conductors 611 b. Thefirst inner conductors can be bare conductors, coated conductorscomprising an inner conductive core and an insulating layer surroundingthe inner conductive core or coaxial cables. The second inner conductorscan be coated conductors comprising an inner conductive core and aninsulating layer surrounding the inner conductive core or coaxial cablesto ensure that they are isolated from one another.

The first dielectric film 620 surrounds a substantial portion of thefirst conductor set such that the base layer of the first dielectricfilm is partially concentric with the first conductor set and wherein aportion of the first protrusions is disposed between the first conductorset and the base layer in the region where the base layer is concentricwith the first conductor set. The first dielectric film comes togetherat pinch portion 650 a forming a first cable sub-unit in the form ofinsulating envelope 640 a around the first conductor set 610 a. The baselayer 622 of the first dielectric film 620 includes three sub-layers, aninsulating sub-layer 623 having the first protrusions formed on a firstmajor surface thereof, a metallic sub-layer 627 disposed adjacent to thesecond major surface of the insulating sub-layer and a protectiveinsulating or jacket sub-layer 628 disposed over the metallic sub-layer.The metallic sub-layer can act as a shielding layer to help ground thehigh speed transmission cable, can help control the impedance of thecable as well as preventing electromagnetic interference emissions fromthe cable.

The first dielectric film 620 is then disposed on either side (i.e. thetop and bottom sides as shown in FIG. 7A) of the second conductor set610 b such that the base layer of the first dielectric film is partiallyconcentric with the second conductor set and wherein a portion of thefirst protrusions is disposed between the first conductor set and thebase layer in the region where the base layer is concentric with thefirst conductor set. The first dielectric film comes together at pinchportion 650 b, 650 c disposed on either side of the conductor setforming a second cable sub-unit in the form of insulating envelope 640 baround the second conductor set 610 b. Transmission cable 600 can haveadditional conductor sets contained in additional cable sub-unitsdisposed beyond pinched portion 650 c.

An optional additional longitudinal member 670 can be disposed betweenpinched portions 650 a, 650 b between the first and second conductorsets. The additional longitudinal member can be a drain wire, an opticalconductor, a strength member and an additional conductor set. When theadditional longitudinal member is a drain wire, the drain wire can beused as a grounding element for the transmission cable.

FIG. 7B illustrates a portion of another exemplary high speedtransmission cable 700 according to an aspect of the present inventionthat includes a first conductor set 710 a, a second conductor set 710 b,a third conductor set 710 c, a first dielectric film 720 and a seconddielectric film 730, wherein each of the first and second dielectriclayers are at least partially concentrically disposed around the first,second, and third conductor sets. The first, second, and third conductorsets each include two parallel inner conductors defining thelongitudinal axis of the transmission cable. The inner conductors can becoated conductors comprising an inner conductive core and an insulatinglayer surrounding the inner conductive core or coaxial cables to ensurethat they are isolated from one another.

The first dielectric film 720 includes a base layer 722 having aplurality of first protrusions formed on a first major surface of thebase layer, wherein the first dielectric film can be disposed such thatthe base layer is partially concentric with the conductor sets andwherein a portion of the first protrusions is disposed between theconductor sets and the base layer in the regions where the base layer isconcentric with the conductor sets.

The second dielectric film 730 can be similar to first dielectric film720 in that the second dielectric film includes a base layer 732 havinga plurality of first protrusions formed on a first major surface of thebase layer. The second dielectric film can be disposed partiallyconcentric with the conductor sets opposite the first dielectric filmsuch that the base layer of the second dielectric film is partiallyconcentric with the conductor sets and wherein a portion of the firstprotrusions of the second dielectric film are disposed between theconductor sets and the base layer of the second dielectric film in theregions where the base layer is concentric with the conductor sets.

The base layers 722, 732 of the first and second dielectric films 720,730 includes three sub-layers, an insulating sub-layer 723, 733 havingthe first protrusions formed on a first major surface thereof, ametallic sub-layer 727, 737 disposed adjacent to the second majorsurface of the insulating sub-layer and a protective insulatingsub-layer 728, 738 disposed over the metallic sub-layer.

The first and second dielectric films are brought together at pinchedportions 750 a, 750 b disposed on either side of first conductor set 710a to form insulating envelope 740 a around the first conductor set; atpinched portions 750 b, 750 c disposed on either side of secondconductor set 710 b to form insulating envelope 740 b around the secondconductor set; and at pinched portions 750 c, 750 d, disposed on eitherside of third conductor set 710 c to form insulating envelope 740 caround the third conductor set. Transmission cable 700 can haveadditional conductor sets disposed beyond pinched portions 750 a, 750 d.

Referring to FIGS. 8A and 8B, shows a schematic representation of onemethod of assembling an exemplary transmission cable 900 in accordancewith the current invention. FIG. 8A shows a conductor set 910 having twoinner conductors, a first dielectric film 920, and a second dielectricfilm 930 that are brought together. Heat and pressure are applied asindicated by arrows 990 to bond the first and second dielectric films toone another in the region on either side of conductor set formingpinched portions 950 shown in FIG. 8B. The heat and pressure melt andflatten the protrusions 924, 934 of the first and second dielectricfilms bonding the films together.

FIGS. 6A-6D, 9A-9D and 10A-10C are a variety of schematic cross-sectionsof a portion of a high speed transmission cable in accordance with thecurrent invention.

FIG. 6A illustrates a portion (e.g. a single insulating envelope 540A)of another exemplary high speed transmission cable that has a metallicshielding layer incorporated into only one side of the construction. Thetransmission cable includes a first conductor set 510, a firstdielectric film 520A and a second dielectric film 530A, wherein each ofthe first and second dielectric films are at least partiallyconcentrically disposed around the first conductor set. The firstconductor set includes two parallel inner conductors 511 defining thelongitudinal axis of the transmission cable. The inner conductors can becoated conductors comprising an inner conductive core 512 and aninsulating layer 514 surrounding the inner conductive core or coaxialcables to ensure that they are isolated from one another.

The first dielectric film 520A includes a base layer 522 having threesub-layers, an insulating sub-layer 523 having a plurality of firstprotrusions 524A formed on a first major surface thereof, a metallicsub-layer 527 disposed adjacent to the second major surface of theinsulating sub-layer and a protective insulating sub-layer 528 disposedover the metallic sub-layer. Metallic sub-layer 527 will act as ametallic shielding layer in the present construction.

The second dielectric layer 530A includes a base layer 532 having twosub-layers, an insulating sub-layer 533 having a plurality of firstprotrusions 534A formed on a first major surface thereof and aprotective insulating sub-layer 538 adjacent to the second major surfaceof the insulating sub-layer.

The first and second dielectric films are brought together at pinchedportions 550A, disposed on either side of first conductor set 510 toform insulating envelope 540A around the first conductor set such thatthe base layers of the first and second dielectric films 520A, 530A arepartially concentric with the conductor sets and wherein a portion ofthe first protrusions 524A, 534A of the first and second dielectricfilm, respectively, are disposed between the conductor set and the baselayer of the respective dielectric film in the regions where the baselayers are concentric with the conductor set. Pinched portions 550A canbe formed along the transverse mid-plane of the transmission cable 595.Alternatively, the pinched portions may be disposed along a plane eitherabove or below the transverse mid-plane of the transmission cable.

The transmission cable can have additional conductor sets disposed oneither side of insulating envelope 540A beyond pinched portions 550A. Inan alternative aspect, the transmission cable can contain the singleconductor set shown in FIG. 6A where pinched portions 550A form theedges of the cable.

FIG. 6B illustrates a portion (e.g. a single insulating envelope 540B)of another exemplary high speed transmission cable having a structureddielectric film 520B on only one side of the first conductor set. Thetransmission cable includes a first conductor set 510, a firstdielectric film 520B and a dielectric layer 560, wherein the firstdielectric film and the dielectric layers are at least partiallyconcentrically disposed around the first, conductor set. The firstconductor set includes two parallel inner conductors defining thelongitudinal axis of the transmission cable as described previously.

The first dielectric film 520B includes a base layer 522 having threesub-layers, an insulating sub-layer 523 having a plurality of firstprotrusions 524B formed on a first major surface thereof, a metallicsub-layer 527 disposed adjacent to the second major surface of theinsulating sub-layer and a protective jacket sub-layer 528 disposed overthe metallic sub-layer.

Dielectric film 560 includes three sub-layers, an insulating sub-layer563, a metallic sub-layer 567 disposed adjacent to a major surface ofthe insulating sub-layer and a protective insulating sub-layer 568disposed over the metallic sub-layer.

Metallic sub-layer 527 in the first dielectric film 520B and themetallic sub-layer 567 of dielectric film 560 will act as metallicshielding layers in the present construction.

The first dielectric film 520B and dielectric film 560 are broughttogether at pinched portions 550B, disposed on either side of firstconductor set 510 to form insulating envelope 540B around the firstconductor set such that the base layer of the first dielectric films520B and dielectric film 560 are partially concentric with the conductorsets and wherein a portion of the first protrusions 524B of the firstdielectric film are disposed between the conductor set and the baselayer of the first dielectric film in the regions where the base layeris concentric with the conductor set. Pinched portions 550B can beformed along the transverse mid-plane of the transmission cable.

The transmission cable can have additional conductor sets disposed oneither side of insulating envelope 540B beyond pinched portions 550B. Inan alternative aspect, the transmission cable can contain the singleconductor set shown in FIG. 6B where pinched portions 550B form theedges of the cable.

FIG. 6C illustrates a portion (e.g. a single insulating envelope 540C)of another exemplary high speed transmission cable having two structureddielectric films 520C, 530C where the protrusions 524C, 534Cinterpenetrate one another in pinched portions 550C on either side offirst conductor set 510. The interpenetrating protrusions mechanicallyinterlock to form insulating envelope 540C. Because the protrusionsremain intact (i.e. they are not melted to form the bond between thefirst and second dielectric films), this construction has the advantagethat the conductor set(s) are easily accessible for termination orseparation in to individual conductors by simply separating the firstand second dielectric films causing the protrusions to release eachother.

The base layers 522, 532 of the first and second dielectric films 520C,530C includes three sub-layers, an insulating sub-layer 523, 533 havingthe first protrusions 524C, 534C formed on a first major surfacethereof, a metallic sub-layer 527, 537 disposed adjacent to the secondmajor surface of the insulating sub-layer and a protective insulating orjacket sub-layer 528, 528 disposed over the metallic sub-layer. Theprotrusions 524C, 534C have a mushroom shape. The cap portion 535 a ofthe mushroom shaped protrusions is larger than the stem portion 535 bsuch that the edges of the cap portion overhang the stem portion. Theedges of the cap portions of the protrusions 524C of the firststructured dielectric film 520C and the edges of the cap portions of theprotrusions 534C of the second structured dielectric film 530C engagewith one another when an adequate pressure is applied to the first andsecond structured dielectric film on either side of the first conductorset 510 to form pinched portion 550C.

FIG. 6D illustrates a portion (e.g. a single insulating envelope 540D)of another exemplary high speed transmission cable wherein the first andsecond dielectric films 520D, 530D are joined together at pinchedportions 550D disposed along a plane below the transverse mid-plane 595of the transmission cable. In addition, first conductor set shown inFIG. 6D has two inner conductors 512 disposed in a single insulatinglayer 514D.

FIGS. 9A-9D illustrate several portions (e.g. insulating envelopes1040A-1040D) of exemplary high speed transmission cables where thestructured dielectric layers have larger second protrusions that can bedisposed between the inner conductors of the conductor set enclosedwithin the insulating envelope. These larger second protrusions canprovide some mechanical stabilization for the inner conductors.

FIG. 9A illustrates a portion (e.g. a single insulating envelope 1040A)of another exemplary high speed transmission cable. The transmissioncable includes a first conductor set 1010, a first dielectric film 1020Aand a second dielectric film 1030A, wherein each of the first and seconddielectric films are at least partially concentrically disposed aroundthe first conductor set. The first conductor set includes two parallelinner conductors 1011 defining the longitudinal axis of the transmissioncable. The inner conductors can be coated conductors comprising an innerconductive core 1012 and an insulating layer 1014 surrounding the innerconductive core or coaxial cables to ensure that they are isolated fromone another.

The base layers 1022, 1032 of the first and second dielectric films1020A, 1030A includes three sub-layers, an insulating sub-layer, ametallic sub-layer disposed adjacent to the second major surface of theinsulating sub-layer and a protective insulating sub-layer disposed overthe metallic sub-layer. In addition, base layers 1022, 1032 include aplurality of first protrusions 1024, 1034 and larger second protrusions1025A, 1035A formed on the major surface of the base layers of the firstand second dielectric films.

The larger second protrusions 1025A, 1035A in FIG. 9A have a trapezoidalcross section and can be in the form of a continuous ridge, adiscontinuous ridge, or as individual posts. The larger secondprotrusions 1025B, 1035B in FIG. 9B have a semi-elliptical cross sectionand can be in the form of a continuous ridge, bumps or individual posts.The larger protrusions in FIG. 9A and 9B can separate and stabilize theinner conductors. The larger protrusions may provide simple mechanicalseparation or can be bonded to the insulation of the inner conductors orto bare conductors if no additional insulation present.

In FIGS. 9C and 9D, the larger protrusions 1025C, 1025D of the firstdielectric films 1020C, 1020D, respectively, interlock with the largerprotrusions 1035C, 1035D of the second dielectric films 1030C, 1030D. Asshown, these protrusions can be used to bond the first and seconddielectric films and to separate the inner conductors. FIG. 9D shows anexemplary portion of (e.g. a single insulating envelope 1040D) of anexemplary high speed transmission cable having a pair of bare innerconductors 1011D.

FIGS. 10A-10C illustrate several portions (e.g. insulating envelopes1140A-1140C) of exemplary high speed transmission cables having aseparator disposed between the inner conductors of the conductor setthat is enclosed within the insulating envelope. These larger secondprotrusions can provide some mechanical stabilization for the innerconductors.

FIG. 10A illustrates a portion (e.g. a single insulating envelope 1140A)of another exemplary high speed transmission cable. The transmissioncable includes a first conductor set 1110, a first dielectric film1120A, a second dielectric film 1130A and a separator 1185A. The firstand second dielectric films are at least partially concentricallydisposed around the first conductor set. The first conductor setincludes two parallel inner conductors 1111 defining the longitudinalaxis of the transmission cable. The inner conductors can be coatedconductors comprising an inner conductive core and an insulating layersurrounding the inner conductive core or coaxial cables to ensure thatthey are isolated from one another.

The base layers of the first and second dielectric films 1120A, 1130Aincludes three sub-layers, an insulating sub-layer having a plurality offirst protrusions 1124A, 1134A formed on a first major surface thereof,a metallic sub-layer disposed adjacent to the second major surface ofthe insulating sub-layer and a protective jacket sub-layer.

Separator 1185A in FIG. 10A has a rectangular cross section. Theseparator can be a continuous member that runs longitudinally betweenthe inner conductors in the first conductor set. In an alternativeaspect, the separator 1185B, shown in FIG. 10B, can have an ellipticalcross section between the inner conductors of conductor set 1110. Whilein another aspect, the separator 1185C, shown in FIG. 10C, can have anannular cross section positioned between two bare inner conductors1111C. The separator can have a cross-section of any geometric shapecompatible with the overall design of the transmission cable. WhileFIGS. 10A-10C show only a single separator disposed between the innerconductors of the conductor set, the transmission cable canalternatively have multiple separators disposed between each innerconductor set.

FIGS. 11A-11B, 12A-12E, and 13A-13D show several variations of a secondembodiment of a high speed transmission cable in accordance with thecurrent invention.

FIG. 11A shows a high speed transmission cable 2000 that includes aconductor set 2010 having two parallel inner conductors 2011 defining alongitudinal axis of the transmission cable, a structured dielectricfilm 2020 at least partially concentrically disposed around theconductor set wherein a section 2021 of the dielectric film is disposedbetween the two parallel inner conductors. The dielectric film includesa base layer 2022 having a plurality of first protrusions 2024 formed ona first major surface of the base layer. The dielectric film enclosesthe conductor set such that the base layer is partially concentric withthe conductor set and wherein a portion of the first protrusions isdisposed between the first conductor set and the base layer. Dielectricfilm 2020 can have one or more second protrusions 2025 formed on thefirst major surface of the base layer. The second protrusions can beused to secure the section of the dielectric film is disposed betweenthe two parallel inner conductors to facilitate manufacturability of thetransmission cable. Optionally, the dielectric film can have one or moreflange portions 2026 that can be used to help facilitate wrapping of thedielectric film by securing the longitudinal edges of the dielectricfilm either between the inner conductors (e.g. flange portions 2026a) orby being wrapped over a portion of the second major surface of thedielectric film (e.g. flange portions 2026b). In an exemplary aspect,one or more of the flange portions, for example flange portion 2026b, ofthe dielectric film can be coated with an adhesive (not shown) to enablethe flange portion to be bonded the second major surface of thedielectric film.

FIG. 11B shows a high speed transmission cable 2100 that is similar totransmission cable 2000 shown in FIG. 11A except that it furtherincludes a protective insulating layer or jacket 2170 that encasesconductor set 2110 wrapped in structured dielectric film 2120. In anexemplary aspect (not shown), jacket may be textured to facilitatelateral bending of the transmission cable. The texturing can take theform of thinned regions, transverse corrugations or slots in the jacketmaterial.

High speed transmission cables 2000, 2100 can be classified as twinaxial cables (also known as twinax cables) wherein two inner conductorsare placed side-by-side within the cable. The structured dielectric filmthat surrounds the inner conductors support and interact strongly withthe electric field when a current travels along the cable. As such,electrical properties of the dielectric film, such as the dielectricconstant and loss, are critical to the signal speed and signal integrityof the transmission cable. These twin axial cable constructions canyield increased velocity of signal propagation, low loss, and lowcapacitance, which enables smaller diameter transmission cables for thesame impedance as conventional cable designs. Because parallel twinaxconductors is a fundamental structure for data transmission lines, thereis a need to manufacture this structure in a cost-effective, efficientmanner while preserving the excellent transmission line characteristicsand mechanical properties of the transmission cable.

FIGS. 12A-12E show several variations on a twinax style high speedtransmission cable in accordance with the current invention. FIG. 12Ashows a cross-section of a high speed transmission cable 2200 thatincludes a conductor set 2210 having two parallel inner conductors 2211defining a longitudinal axis of the transmission cable, and a structureddielectric film 2220 at least partially concentrically disposed aroundthe conductor set. The first inner conductors in the conductor set canbe bare conductors, coated conductors comprising an inner conductivecore and an insulating layer surrounding the inner conductive core orcoaxial cables.

Dielectric film 2220 includes a plurality of first protrusion 2224extending from a portion of the first major surface of the dielectricfilm. The dielectric film includes flange portions 2226 adjacent to thelongitudinal edges of the dielectric film. The flange portions areadjacent to the section 2221 of the dielectric film disposed between thetwo inner conductors. The flange portions of the dielectric film arefree of protrusions. The flange portions 2226 are folded back on eachother to secure sections 2221 between the inner conductors.

High speed transmission cable 2200 can further include an outerconductor such as shielding layer 2265 surrounding conductor set 2210wrapped in structured dielectric film 2220. A protective jacket orinsulating layer 2270 encases the shielding layer.

Optionally, high speed transmission cable 2200 can further include anadditional longitudinal member. In an exemplary aspect, the additionallongitudinal member can be in the form of a drain wire 2266 extendingparallel to the plurality of spaced apart inner conductors 2211.Alternatively, the additional longitudinal member can be an opticalconductor, a spacer, a strength member, or an additional conductor set.

FIG. 12B is a cross-section of a high speed transmission cable 2300 thatincludes a conductor set 2310 having two bare parallel inner conductors2311 defining a longitudinal axis of the transmission cable, astructured dielectric film 2320 at least partially concentricallydisposed around the conductor set. The dielectric film includes flangeportions 2326 adjacent to the longitudinal edges of the dielectric filmand adjacent to section 2321 of the dielectric film disposed between thetwo inner conductors. The flange portions wrap under the innerconductors securing sections 2321 between the inner conductors.

FIG. 12C is a cross-section of a high speed transmission cable 2400 thatincludes a conductor set 2410 having two bare parallel inner conductors2411 defining a longitudinal axis of the transmission cable, astructured dielectric film 2420 at least partially concentricallydisposed around the conductor set.

Dielectric film 2420 includes a plurality of first protrusion 2424extending from a portion of the first major surface of the dielectricfilm and at least one larger protrusion 2425 disposed near eachlongitudinal edge of the dielectric film. The larger protrusions canhelp anchor sections 2421 between the inner conductors.

Optionally, exemplary transmission cable 2500, shown in FIG. 12D, caninclude at least one additional longitudinal member 2575 extendingparallel to the plurality of spaced apart conductor sets. The additionallongitudinal member can be a wire, monofilament or stranded materialformed from a polymer such as nylon, Kevlar or other polymer resinhaving the desired insulating properties. Alternatively, thelongitudinal member may be made of metal as would be the case if theadditional longitudinal member was a drain wire. The shape of additionallongitudinal member can be rectangular, elliptical or other polygonalcross-section depending on the design and application of the resultingtransmission cable.

FIG. 12E shows a cross-section of a high speed transmission cable 2600that includes a conductor set having two bare parallel inner conductorsdefining a longitudinal axis of the transmission cable, a structureddielectric film 2620 at least partially concentrically disposed aroundthe conductor set. The longitudinal edges of the dielectric film areanchored by an adhesive 2687 to secure sections 2621 between the innerconductors.

Referring to FIG. 13A, high speed transmission cable 2700 includes aconductor set 2710 having two parallel inner conductors defining alongitudinal axis of the transmission cable, a structured dielectricfilm 2720 at least partially concentrically disposed around theconductor set wherein a section 2721 of the dielectric film is disposedbetween the two parallel inner conductors. The dielectric film includesa base layer 2722 having a plurality of first protrusions 2724 formed ona first major surface of the base layer. Dielectric film 2720 can haveone or more secondary protrusions 2725 formed on the first major surfaceof the base layer. The secondary protrusions can be used to securesection 2721 of the dielectric film.

Similarly, high speed transmission cables 2800, 2900 shown in FIGS. 13Band 13C include different forms of the second protrusions 2825, 2925 tosecure section 2821, 2921 of dielectric film 2820, 2920 between the pairof inner conductors.

Referring to FIG. 13D, high speed transmission cable 3000 includes aconductor set 3010 having two parallel inner conductors defining alongitudinal axis of the transmission cable, a structured dielectricfilm 3020 at least partially concentrically disposed around theconductor set wherein a section 3021 of the dielectric film is disposedbetween the two parallel inner conductors. The dielectric film 3020includes a base layer 3022 having a plurality of first protrusions 3024formed on a first major surface of the base layer. Dielectric film 3020can have secondary protrusions 3025 formed along the midline 3096 of thedielectric film on the first major surface of the base layer and aplurality of third protrusions disposed on the second major surface ofthe base layer adjacent to the longitudinal edges 3027 of the dielectricfilm. The second protrusions 3025 and third protrusions 3023 can beshaped to intermate with one another to secure sections 3021 between thepair of inner conductors.

In order to make the exemplary transmission cables shown in FIGS.12A-12E and 13A-13D, the dielectric film and the inner conductors canfed into a forming tool or die 3100 as shown in FIG. 14. The formingtool has three zones: an entrance zone 3120, a wrapping zone 3140, andan exit zone 3160.

The entrance zone 3120 takes the dielectric film 3220 and begins to foldthe longitudinal edges 3221 a, 3221 b of the dielectric film up andaround the inner conductors 3211 as shown in FIG. 15A, which is across-sectional view of the forming tool along reference line A-A inFIG. 14. The entrance zone of the forming tool includes a first bodyportion 3130 having a trough 3125 formed in a surface thereof. Thetrough varies in width and depth along the length of the entrance zone.The trough can be fairly wide and shallow at the first end 3122 ofentrance zone 3120 becoming narrower and deeper at the second end 3124of the entrance zone.

The wrapping zone 3140 can urge the longitudinal edges 3221 a, 3221 b ofthe dielectric film 3220 between the pair of inner conductors 3211 whilesimultaneously moving the inner conductors closer to one another asshown in FIGS. 15B and 15C. The wrapping zone includes a second bodyportion 3150 having a passageway 3145 extending from a first end 3142 ofthe wrapping portion to the second end 3144 of the wrapping portion.FIG. 15B is a cross-sectional view of the forming tool along referenceline B-B in FIG. 14 at the first end of the wrapping zone. FIG. 15C is across-sectional view of the forming tool along reference line C-C inFIG. 14 at the second end of the wrapping zone. Passageway 3145 includestwo overlapping lobe portions 3146 a, 3146 b. The overlapping lobeportions can be generally funnel shaped having the large end of thefunnel shape at the first end of the wrapping portion and the small endof the funnel shape at the second end of the wrapping portion.

The exit zone 3160 supports the pair of inner conductors 3211 wrapped inthe dielectric film 3220 while the outer conductor 3266, if applicable,is placed in the valley between the two dielectric wrapped innerconductors as shown in FIG. 15D, which is a cross-sectional view of theforming tool along reference line D-D in FIG. 14.

Additional layers (not shown) such as shielding layers, dielectriclayers or an outer jacket layer can be formed around the dielectricwrapped inner conductors by conventional processes such as wrapping,braiding, taping, overcoating, extrusion, molding, etc.

Once the transmission cable is created, it can be combined with one ormore other transmission cable sub-units to form a higher orderstructured cable for use in a cable assembly. The higher order cables orassemblies can have electrical and mechanical performance benefits overcables having a single sub-unit.

Following are exemplary embodiments of a high speed transmission cableaccording to aspects of the present invention.

Embodiment 1 is a high speed transmission cable comprising a firstconductor set including one or more inner conductors defining alongitudinal axis of the transmission cable; a dielectric filmcomprising a base layer having a plurality of first protrusions formedon a first major surface of the base layer, the dielectric film havingfirst and second longitudinal edges aligned with the first conductorset; wherein the dielectric film is disposed such that the base layer ispartially concentric with the first conductor set and wherein a portionof the first protrusions is disposed between the first conductor set andthe base layer in a region where the base layer is concentric with thefirst conductor set; and a pinched portion forming an insulatingenvelope around the first conductor set.

Embodiment 2 is the transmission cable of embodiment 1, furthercomprising a second dielectric film that includes a second base layer,the second base layer is disposed partially concentric with the firstconductor set.

Embodiment 3 is the transmission cable of embodiment 2, wherein thesecond dielectric film further comprises a plurality of protrusionsformed on a first major surface of the second base layer.

Embodiment 4 is the transmission cable of embodiment 3, wherein theplurality of protrusions formed on the second base layer of the seconddielectric film are the same as the first protrusions formed on thefirst base layer of the first dielectric film.

Embodiment 5 is the transmission cable of embodiment 1, wherein thefirst base layer of the first dielectric material is selected from oneof an insulating film, a metal foil, a bilayer structure composed of aninsulating film and a metal layer, and other multilayer structurecombinations of insulating layers and conductive layers.

Embodiment 6 is the transmission cable of embodiment 2, wherein thesecond base layer of the second dielectric material is selected from oneof an insulating film, a metal foil, a bilayer structure composed of aninsulating film and a metal layer, and other multilayer structurecombinations of insulating layers and conductive layers.

Embodiment 7 is the transmission cable of any of the previousembodiments, further comprising protective insulating layer disposedadjacent to a second major surface of at least one of the firstdielectric film and the second dielectric film.

Embodiment 8 is the transmission cable of embodiment 7, furthercomprising an outer conductor disposed between at least one of theprotective insulating layer and the first dielectric film and theprotective insulating layer and the second dielectric film.

Embodiment 9 is the transmission cable of embodiment 1, furthercomprising at least one additional longitudinal member extendingparallel to the first conductor set.

Embodiment 10 is the transmission cable of embodiment 9, wherein the atleast one additional longitudinal member is disposed in the insulatingenvelope with the first conductor set.

Embodiment 11 is the transmission cable of embodiment 9, wherein the atleast one additional longitudinal member is spaced apart from the firstconductor set by the pinched portion.

Embodiment 12 is the transmission cable of embodiments 9-11, wherein theat least one additional longitudinal member is one of a groundconductor, an optical conductor, a strength member and an additionalconductor set.

Embodiment 13 is a transmission cable comprising: a plurality of spacedapart conductor sets arranged generally in a single plane, eachconductor set including one or more substantially parallel longitudinalinsulated conductors; a dielectric film comprising a base layer having aplurality of first protrusions formed on a first major surface of thebase layer, the dielectric film having first and second longitudinaledges aligned with the first conductor set; wherein the dielectric filmis disposed such that the base layer is partially concentric with thefirst conductor set and wherein a portion of the first protrusions isdisposed between the first conductor set and the base layer in a regionwhere the base layer is concentric with the first conductor set; and apinched portion disposed between each of the plurality of spaced apartconductor sets.

Embodiment 14 is the transmission cable of embodiment 13, furthercomprising at least one additional longitudinal member extendingparallel to the plurality of spaced apart conductor sets.

Embodiment 15 is the transmission cable of embodiment 14, wherein the atleast one additional longitudinal member is disposed in the insulatingenvelope with at least one of the plurality of spaced apart conductorsets.

Embodiment 16 is the transmission cable of embodiment 14, wherein the atleast one additional longitudinal member is spaced apart at least one ofthe plurality of spaced apart conductor sets by the pinched portion.

Embodiment 17 is the transmission cable of embodiments 16-18, whereinthe at least one additional longitudinal member is one of a groundconductor, an optical conductor, a strength member and an additionalconductor set.

Embodiment 18 is a high speed transmission cable comprising a firstconductor set including two parallel inner conductors, and a dielectricfilm comprising a base layer having a plurality of first protrusionsformed on a first major surface of the base layer, wherein thedielectric film is disposed such that the base layer is partiallyconcentric with the conductor set such that a portion of the firstprotrusions is disposed between the first conductor set and the baselayer in a region where the base layer is concentric with the conductorset and wherein a portion of the dielectric film is disposed between theinner conductors.

Embodiment 19 is the transmission cable of embodiment 18, wherein thedielectric film has a first longitudinal edge aligned with the firstconductor set and disposed between the inner conductors of the firstconductor set.

Embodiment 20 is the transmission cable of embodiment 18, furthercomprising a protective jacket formed on the outside of the high speedtransmission cable over the wrapped dielectric film.

Embodiment 21 is the transmission cable of embodiment 18, furthercomprising an outer conductor disposed between the dielectric film andthe protective jacket.

Embodiment 22 is the transmission cable of embodiment 21, wherein theouter conductor is a drain wire.

Embodiment 23 is the transmission cable of embodiment 18, wherein theouter conductor is a shielding layer.

Embodiment 24 is the transmission cable of embodiment 18, wherein thebase layer of the dielectric film is selected from one of an insulatingfilm, a metal foil, a bilayer structure composed of an insulating filmand a metal layer, and other multilayer structure combinations ofinsulating layers and conductive layers.

Embodiment 25 is the transmission cable of embodiment 18, wherein thefirst protrusions are one of a post, a continuous ridge, a discontinuousridge, a bump, a pyramid and any other three dimensional polygonalshape.

Embodiment 26 is the transmission cable of embodiment 18, wherein thedielectric film has a flat flange portion disposed adjacent to at leastone of a first longitudinal edge and a second longitudinal edge and atextured portion that includes the first protrusions.

Embodiment 27 is the transmission cable of embodiment 26, wherein theflat flange portion is integrally formed with the dielectric film.

Embodiment 28 is the cable of embodiments 26 or 27, wherein the flatflange portion secures portion of the dielectric film is disposedbetween the inner conductors.

Embodiment 29 is the transmission cable of embodiment 18, furthercomprising a dielectric separator element disposed the inner conductors.

Embodiment 30 is the transmission cable of embodiment 18, wherein theinner conductors comprise one of an insulated metallic wire and a bareconductor.

Embodiment 31 is the transmission cable of embodiment 18, furthercomprising at least one additional longitudinal member extendingparallel to the first conductor set.

Embodiment 32 is the transmission cable of embodiment 31, wherein the atleast one additional longitudinal member is one of a ground conductor,an optical conductor, a strength member and an additional conductor set.

Embodiment 33 is the transmission cable of embodiment 10, furthercomprising a second protruding structure formed on the base layer of thedielectric film wherein the second protruding structure can be one of adielectric separator and a securing device for anchoring the portion ofthe dielectric film is disposed between the inner conductors.

Although specific embodiments have been illustrated and described hereinfor purposes of description of the preferred embodiment, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent implementations calculated to achieve thesame purposes may be substituted for the specific embodiments shown anddescribed without departing from the scope of the present invention.Those with skill in the mechanical, electro-mechanical, and electricalarts will readily appreciate that the present invention may beimplemented in a very vide variety of embodiments. This application isintended to cover any adoptions or variations of the preferredembodiments discussed herein. Therefore, it is manifestly intended thatthis invention be limited only by the claims and the equivalentsthereof.

What is claimed is:
 1. A high speed transmission cable comprising aconductor set comprising two parallel uninsulated conductors extendingalong a length of the cable; and first and second dielectric filmsdisposed on opposite sides of the cable and comprising concentricportions partially concentric with the conductor set and pinchedportions on each side of the conductor set, the pinched portions of thefirst and second dielectric films bonded to one another on each side ofthe conductor set, each dielectric film comprising: a base layer; and aplurality of shorter protrusions and a taller protrusion disposed on amajor surface of the base layer only in the concentric portion of thedielectric film between the pinched portions of the dielectric film, theshorter protrusions disposed between the conductor set and the baselayer so that at least some of the shorter protrusions contact the twouninsulated conductors, wherein the taller protrusions of the first andsecond dielectric films are disposed between and separate the twouninsulated conductors and are bonded to, or interlocked with, eachother.
 2. The transmission cable of claim 1, wherein the tallerprotrusions of the first and second dielectric films are bonded to eachother.
 3. The transmission cable of claim 1, wherein the tallerprotrusions of the first and second dielectric films are interlockedwith each other.